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Mid-Thoracic Upper Instrumented Vertebrae in Adult Spinal Deformity: A Viable Stopping Point?
Anthony E Bishay1, Harsh Jain2, Hani Chanbour2
1School of Medicine, Vanderbilt University, Nashville, TN.
Study Design:
Single-institution retrospective cohort study.
Objective:
To compare patients undergoing ASD surgery with an upper instrumented vertebrae (UIV) in the upper-thoracic, mid-thoracic, or lower-thoracic spine regarding: (1) preoperative factors, (2) perioperative variables, and (3) postoperative outcomes.
Background:
The classic teaching in adult spinal deformity surgery (ASD) is to avoid stopping a construct in the mid-thoracic spine; however, this theory remains untested.
Materials And Methods:
Patients undergoing ASD surgery from 2009 to 2021 with a 2-year follow-up were reviewed. Standard demographic, radiographic, and perioperative data were collected. The primary independent variable was UIV location: upper-thoracic: C7-T4, mid-thoracic: T5-T8, and lower-thoracic: T9-L2. Outcomes included mechanical complications, reoperations, and patient-reported outcome measures.
Results:
Of 190 patients, the UIV region was: 29 (15.3%) upper-thoracic UIV, 42 (22.1%) mid-thoracic, and 119 (62.6%) lower-thoracic. Preoperatively, mid-thoracic UIV patients were older than upper-thoracic UIV (71.7±10.8 vs . 60.6±14.1, P <0.001). Perioperatively, mid-thoracic UIV had higher estimated blood loss than both upper-thoracic ( P =0.047) and lower-thoracic ( P <0.001) groups. Radiographically, C7-plumb line (C7PL) correction was greater in mid-thoracic versus lower-thoracic UIV (27.9±28.0° vs . 16.8±17.7°, P =0.045). Postoperatively, mid-thoracic UIV had higher rates of pseudarthrosis (47.6% vs . 20.7%, P =0.021), reoperation for mechanical complications (50.0% vs . 20.7%, P =0.012), and reoperation for any reason (52.4% vs . 20.7%, P =0.007) versus upper-thoracic UIVs. Compared with lower-thoracic UIVs, mid-thoracic UIVs had higher rates of pseudarthrosis (47.6% vs . 28.6%, P =0.025) and rod fracture (38.1% vs . 20.2%, P =0.021). No difference was found in proximal junctional kyphosis/failure or PROMs.
Conclusion:
Mid-thoracic UIVs had higher rates of pseudarthrosis and both mechanical and all-cause reoperations compared with upper-thoracic UIVs, as well as higher rates of pseudarthrosis and rod fractures compared with lower-thoracic UIVs. The only superior outcome of a mid-thoracic UIV was greater coronal C7PL correction versus lower-thoracic UIV. These findings suggest stopping ASD constructs in the mid-thoracic spine may yield worse outcomes and should be approached cautiously.
